Dynamic railway track inspecting apparatus



July 16, 1968 L. R. LOMBARDO 3,392,451

DYNAMIC RAILWAY TRACK INSPECTING APPARATUS Filed June 28, 1966 2Sheets-Sheet l INVENTOR. 50 A. 04/5/4200 w aaotd M XW July 16, 1968 L.R. LOMBAIIRDO 3,392,451

DYNAMIC RAILWAY TRACK INSPECTING APPARATUS Filed June 28, 1966 2Sheets-Sheet z Imp/Made r Pu/Je 70 Amp. flezecfor 5' 7 70 Amp- .DeZecfor 56 INVENTOR. .450 P. ZOMBA F00 M MW;

United States Patent 1 3,392,451 DYNAMIC RAILWAY TRACK INSPECTINGAPPARATUS Leo R. Lombardo, Mayfield Heights, Ohio, assignor to ClevelandTechnical Center, Inc., Cleveland, Ohio, a

corporation of Delaware FiledJune 28, 1966, Se'r. No. 561,163 13 Claims.(Cl. 33-145) ABSTRACT OF THE DISCLDSURE rejected.

This invention relates to measuring irregularities in the rails ofrailway track and more'particularly to a dynamic railway trackinspecting apparatus employing electronic systems.

It is known in the art to employ railway track inspecting apparatus forsensing the vertical movements of a vehicle wheel on one track relativeto a vehicle Wheel on the other track. Apparatus of this type isdisclosed in such US. patents as Sperry Patent 1,837,633, Breznai Patent2,978,904 and Grossman Patent 3,038,332. These prior forms of apparatus,however, are predominantly mechanical and are relatively expensive andcomplex. Further, these systems require extensive mechanical apparatusin addition to that normally provided to support a car body. Further,these systems often require complicated apparatus such as gyroscopes tocompensate for the transverse rolling movement of the car body relativeto the wheels. Alternatively, a measuring carriage is required which issupported on the road independently of the car bodyand the car bodysupporting Wheels.

Accordingly, it is an object of this invention to provide a dynamicrailway track inspecting apparatus which is simple and economical inconstruction.

Another object of this invention is to provide a dynamic railway tracktesting system which can be quickly and easily installed and whichutilizes the existing wheels and wheels suspension system of a railwaycar to determine the condition of the track.

A still further object of this invention is to provide a railway tracktesting apparatus which provides an indication of the relative conditionof the railway track tested, which indication can be interpreted by arelatively unskilled worker.

Yet a further object of this invention is to provide simple railwaytrack testing apparatus that automatically records a numericalindication of the relative condition of the railway track andautomatically rejects indications caused by transverse car body roll.

' Briefly, acording to this invention a railway track testing apparatusis provided that comprises an electrical generating system whichgenerates electrical signals indicative .of the difference in thevertical movements of the wheels of a pair of axially-aligned wheelswith respect to a car body. From these generated signals, signals of apredetermined minimum frequency are selected or passed by a filter toone or more signal amplitude responsive circuits. Because transverse carbody roll occurs at a relative low frequency, electrical signalsgenerated by body roll will have a corresponding low frequency and icewill be attenuated or rejected by the filter because the filter has alow frequency cut-01f above the car body roll frequency. Each of aplurality of counters is coupled to the output of one of the amplituderesponsive circuits and the resultant count of any one counter is anindication of the number of signals of that predetermined amplitudewhich have been generated. solely by the relative vertical movement ofthe wheels and independent of signals generated by car body roll.

Advantageously, a pair of transducers may be mounted on the car body.Each transducer is preferably mounted in cantilever fashion and carriesa pair of strain gauges. These transducers are mechanically linked toopposite sides of a conventional truck, as through a pulley and flexiblestrand, to bend in response to vertical movements of one side of thetruck relative to the other side of the truck. Also advantageously, thestrain gauges act as variable resistors. These strain gauges areconnected in a bridge circuit which includes a source of direct current.The output of the bridge is taken from the points intermediate t-hepairs of strain gauges and fed to an amplifier input circuit. Thisbridge output circuit algebraically combines currents caused bymovements of the transducers relative to each other. The strain gaugeson each transducer are serially connected across the source. Be cause ofthe simple nature of the transducers, and the manner of mechanicallybending same, these transducers may be mounted on any existing car body.These and various other objects and features of the invention will bemore clearly understood from the detailed description of the inventionin conjunction with the drawings in which:

FIGURE 1 is a fragmentary side view in elevation showing a portion of acar body and a truck employed in this apparatus;

FIGURE 2 is a fragmentary end view in elevation of the structure ofFIGURE 1 taken from the left-hand side of FIGURE 1 with portionsremoved;

FIGURES 3a and 3b are side elevational and plan views respectively, toan enlarged scale of the transducers employed in FIGURE 1 FIGURE 4 is acombined schematic and block diagram of the electrical portion of therailway track testing apparatus according to one illustrative embodimentof this invention;

FIGURE 5 is a schematic diagram of a portion of the electricalarrangement of FIGURE 4; and,

FIGURE 6 is a schematic representation of the remaining portion of theapparatus indicated in block form in FIGURE 4.

Referring now to the drawing, FIGURES 1 and 2 are a side view inelevation and an end view in elevation, respectively, of an installationof portions of the dynamic railway track testing apparatus according toone embodiment of this invention. In these figures, a car body 10 ismounted on a railway truck 11 by means of the usual mounting means 12and the truck is supported on a pair of axles 13, 14 in the usualmanner. The truck includes the usual springs 15 which permit verticalmovements of the truck frame 11 relative to the car body 10. Each axlehas secured thereto the usual pair of rail-engaging wheels, such aswheels 16 and 17 on axle 13. These wheels engage a pair of rails 18, 19,respectively, which rails are to be tested or inspected by the apparatusaccording to this invention. Advantageously, the railway track testingapparatus includes a pair of transducers 20, 21 each mounted on .asuitable angle bracket 22, 23, respectively, in a cantilever fashion onthe bottom 24 of the body 10 and projecting generally transverselyrelative to the car body 10.

Each transducer is connected to an end of the axle 13 by a mechanicalarrangement which normally places the transducers under substantiallyequal tension. For transducer this arrangement includes a wire ropepassing over a pulley 26 secured by .a suitable bracket 27 to the bottom24 of the car body 10. The wire rope 25 is connected to journal box forthe left end of the axle 13, as viewed in FIGURE 2. Similarly, thetransducer 21 is coupled to journal box 37 on the right-hand end of axle13, as viewed in FIGURE 2, by means of a wire rope 28 passing over asuitable pulley 29 in the same direction as the wire rope 25 passes overthe pulley 26.

With this mechanical coupling between the transducers 20, 21 and theopposite ends of the axle 13, vertical movement of the wheels 16, 17 inthe same direction will produce movements or deflections of thetransducers 20, 21 in the same direction relative to the longitudinaldimension of car body 10. For example, if both ends of axle 13 movedownwardly, both transducers 20, 21 will be defiected to the rightrelative to the view of FIGURE 1. Similarly, vertically upward movementsof both wheels 16 and 17 relative to body 10 will produce deflection ofthe transducers 20, 21 to the left as viewed in FIGURE 1. The electricalportions of transducers 20, 21 are connected to effectively cancel theeffects of these simultaneous movements of the transducers in the samedirection, in a manner which will be subsequently described. Thus themovements of the transducers 20, 21 will be indicative of only thevertical movement of wheel 15 relative to wheel 16 resulting fromrelative undulations of the rails 18 and 19, respectively. Also themagnitude of these movements and the resulting amplitude of thetransducergenerated signals will be proportional to the magnitude ofthese undulations. Transducers 20, 21 are identical and accordingly onlytransducer 20 is shown in FIGURES 3a and 3b, respectively. Transducer 20is in this particular example a relatively thin strip of fiberglasspreferably of the order of of an inch in thickness having a width of 1inch and a length of approximately 13 inches. The transducer 20 includesa base section 32 which is secured to the mounting bracket 22 by meansof a suitable bolting arrangement in which bolts pass through the holes33, 34 in the base section 32 and the transducer 20 is mounted incantilever fashion to bend in a horizontal plane relative to a verticalline 35. Strain gauges 36 and 38 are mounted identical distances fromthe vertical line 35 on opposite sides of the fiberglass strip 31. Thesestrain gauges may be any known type of strain gauge which acts as avariable resistance, the resistance of which varies as a function of thebending of the strain gauge relative to its longitudinal axis. Oneexample of this type strain gauge is shown and described in detail inGeyling Patent 3,023,627.

The resistance of strain gauge 36, shown in full lines in FIGURES 3a and3b, decrease as the eyelet 42 is pulled downwardly relative to the viewof FIGURE 3b and the resistance of strain gauge 38 increases in value bythis same movement. Conversely, movement of the eyelet upwardly relativeto the view of FIGURE 312 causes the resistance of strain gauge 36 toincrease and causes the resistance of strain gauge 38 to decrease. Thecoupling between the wire rope and the end of the transducer remote frombase section 32 will now be described in detail.

The opposite end of the fiberglass strip 31 from the base section 32 isprovided with an oval slot 40 which receives a suitable double eyelet 42which may be longitudinally, slidably held relative to the strip 31 byany suitable means such as a pair of opposed collars 43. With thisarrangement, the eyelet 42 slides in the slot 40 to prevent longitudinalloading of the strip 31. Stated in another manner, the eyelet 42 is freeto move along slot 40 to compensate for the change in radius as strip 31is deflected. The transducers 20 and 21 are each placed under tension bya length of elastic shock cord 44 which is connected to the other sideof the double eyelet 42 and to a suitable anchor 45 on the body 10.

A corresponding pair of strain gauges 46 and 48 mounted on thetransducer 21 are connected to the strain gauges 36 and 38 to define abridge circuit, as shown in the left-hand portion of FIGURE 4. A battery47 is connected between two of the diagonals of the bridge circuit andthe other diagonals of the bridge circuit are connected as input leadsto a preamplifier 50. Thus the variations in the resistances of thestrain gauges in the bridge circuit cause currents in the respectivelegs of the bridge which are algebraically combined at the bridgediagonals. Changes in one leg which are not accompanied by correspondingvariations in the opposite leg of the bridge circuit will result in thegeneration of current which will flow into the input of the preamplifier50. This bridge arrangement of the strain gauges and the direct currentsource 47, therefore, constitute a means for algebraically combiningelectrical signals indicative of the relative vertical movement of thewheels 15, 16.

The output of the bridge circuit fed to the preamplifier 50 is a complexwave form containing information indicative of car body roll andrelative vertical wheel movement. At speeds above 35 miles per hour, thecar body roll component is in a frequency range usually below one cycleper second and the relative vertical wheel movement component is in thefrequency range above two cycles per second. The roll frequency isconstant at all speeds for a given car and is determined by the mass ofthe car and the spring constant. The frequency of cross level variationsvaries with speed and is above 2 c.p.s. at speeds greater than 35 milesper hour. This complex signal is amplified by the preamplifier 50 and isfed to a high pass type filter 52 which has a cut-off frequency of 1 /2cycles per second. Thus high pass type filter 52 will attenuate signalsof a frequency below 1 /2 cycles per second, which includes thosesignals indicating car body roll. High pass filter 52 will, however,transmit the signals indicative of cross level variations to a DCamplifier 54.

The output of DC amplifier 54 is fed to the input .of three separateamplitude detector circuits 56, 57 and 58, each having its inputadjusted to respond to a different signal amplitude. The outputs ofamplitude detectors 56, 57 and 58 are individually connected toindividual pulse counters 60, 61 and 62, respectively. These pulsecounters will each indicate a count, preferably in digital form, of thenumber of pulses which have been detected by the respective amplitudedetectors 56, 57 and 58. Thus the count of the pulse counter 60, 61 and62 will in fact be a relative indication of the road level, whichdigital indication will be simple to understand and will not require theinterpretation by a skilled technician as would be the case if it were acomplex wave form or a multi-frequency wave form. Further, the pulsecounter will deliver an indication of the roadway condition independentof car body roll and car body vertical movements because the effects ofthe car body roll have been eliminated by the high pass filter 52 andthe effects of car body vertical movement are cancelled by the straingauge bridge connection.

As stated above, the car body roll frequency does not vary with speed.Therefore, only filter 52 with a cut-off frequency of 1 /2 cycles persecond is needed. The system will work at any speed greater than 35miles per hour without any modifications to filter 52.

FIGURE 5 and 6, when placed end to end with FIGURE 5 to the left andFIGURE 6 to the right, constitute a schematic representation of portionsof one embodiment of this invention shown in block diagram in FIGURE 4.The terminals 49, 51 correspond to the input terminals to thepreamplifier 50 and the output terminals from the gauge bridge circuitshown in FIGURE 4, with terminal 51 being the common ground for thesystem. The preamplifier includes a pair of transistors 70, 71 connectedin a direct current amplifying arrangement with a source of potential ofapproximately 12 volts applied between terminal 72 and common groundterminal 51. The base of transistor is biased by a pair of resistors 75,76 connected in series between terminals 72 and 51 and with theintermediate point connected to the base of transistor 70. A de-couplingresistor 77 is connected between terminals 49 and the base of transistor70. The collector of transistor 70 is connected to positive batteryterminal 72 to a suitable resistor 78. The resistor 78 includes part ofa base biasing network for transistor 71 which includesserially-connected resistors 79 and 80 with the base of transistor 71connected intermediate these resistors. The emitter of transistor 70 isconnected to the common ground 51 through a resistor 81. The collectorof transistor 71 is connected to the positive battery terminal 72 bymeans of a resistor 84. The emitter of transistor 71 is connected to theground 51 through a suitable resistor 86. The output of this two-stagedirect current amplifier is fed to the input terminals 85, 51 of thehigh pass filter 52.

A shunt capacitor 88 is connected across the input terminals 85, S1 of ahigh pass filter 52. High pass filter 52 includes a series of threeserially-connected capacitors 92, 93 and 94 serially connected betweenthe filter input terminal 85 and a filter output terminal 95. A pair ofshunt arms are connected from the points intermediate these series ofcapacitors to ground 51 and include a first inductance 96 and aserially-connected resistor 97 and a second inductance 98 and itsserially-connected resistor 99. A capacitor 100 is connected in shuntacross the output terminals 95, 51 of high pass filter 52, whichterminals are also the input terminals of amplifier 54. Capacitors 88,100 provide a high frequency cut-01f for the filter. The capacitorseffectively flatten out the response of the filter for a high frequencyroll-01f type response.

Amplifier 54 is a differential amplifier producing an output that can bepositive or negative with respect to ground. This amplifier includes apair of transistors 101, 102 connected in a well-known differentialamplifier arrangement. This differential amplifier arrangement isdescribed in detail on p. 111 of the 1964 edition of General ElectricTransistor Manual. The principal distinction of the instant differentialamplifier from that shown in the text is the grounding of the base oftransistor 102 through a resistor 109. In the instant differentialamplifier, the input terminal 95 is connected to the base of transistor101 through a resistor 103 and the collector of transistor 101 isconnected to a suitable positive battery terminal 72 through a resistor104. The emitter of transistor 101 is connected to a source of negativepotential indicate-d by terminal 110 through a pair of resistors 105,106. Transistor 102 has its emitter connected through a resistor 107 andresistor 106 to the negative terminal 110. As previously mentioned, thebase of transistor 102 is connected to ground through a resistor 109 andthe collector is connected through a resistor 108 to the source ofpositive potential.

The output of this differential amplifier is taken from the collector oftransistor 101 and is fed through the bridge rectifier 55.

Rectifier bridge 55 includes a pair of rectifiers 112, 113 connected tothe collector electrode of the transistor 101 and a second pair ofrectifiers 114, 115 all connected in a well-known bridge structure todeliver a direct current output from terminals 116, 117 in a mannerwellknown in the art. Terminal 116 is the effective ground for theamplitude detector circuit while terminal 117 is the other outputterminal connected to the other detector circuits. Because of theidentity of the amplitude detector circuits 56, 57 and 58, onlyamplitude detector 56 will be described in detail.

The amplitude detector 56 includes three transistors 118, 119 and 120connected in cascade. Negative potential is supplied to thesetransistors from a source indicated by a terminal 121. Transistor 118has its base connected to a variable resistor 122, which variableresistor is connected in series with a resistor 123, the seriescombination being connected between the negative terminal 121 and theeffective ground terminal 116. The variable tap of resistor 122 isconnected to the signal input terminal or signal output terminal 117 ofthe bridge rectifier 55. The

collector electrode of transistor 118 is connected to the source ofnegative potential 121 through a suitable resistor 124. The resistor 124is part of a voltage divider including serially-connected resistors 125and 126. Resistor 126 is connected to the capacitive ground terminal 116previously described. The emitters of transistors 118, 119 are connectedto the effective ground through a resistor 127. The base of transistor118 is connected to the voltage divider 124, 125, 12-6 at a pointintermediate resistors 125 and 126. The collector of transistor 119 isconnected to the negative terminal 121 through a suitable resistor 128.The output of the transistor 119 is fed through a serially-connectedresistor 130 connected between the collector of transistor 119 to thebase of transistor 120. The emitter of transistor 120 is directlyconnected to the negative terminal 121 and the collector of transistor121 is connected to ground terminal 116 through a suitable resistor 132.The output of transistor 120 is taken from the collector and is fedthrough a serially-connected resistor 133 to the base of transistor 134.The emitter of transistor 134 is connected to ground terminal 116 andthe collector through a suitable solenoid 135 to a source of negativepotential indicated by a terminal 136. Solenoid 135 is a part of pulsecounter 60 and actuates a suitable counting mechanism of any convenientform.

Adjusting the position of the variable tap on the resistor 122, variesthe amplitude level at which the amplitude detector transistor 118 willtrigger in response to signals delivered from terminals 116, 117 ofrectifier bridge 55. In setting the resistors corresponding to resistor122 in each of amplitude detectors 57, 58, the settings are preferablystep-wise settings such that each successive amplitude detector requiresa higher level of input signal to trigger the respective amplitudedetector. For example, transistor 118 may be biased by adjusting the tapon the resistor 122 such that the transistor 118 triggers in response toan input signal of 2 volts. Similarly, the resistor corresponding toresistor 122 in amplitude detector 57 may be set so that the transistorcorresponding to transistor 118 in amplitude detector 57 responds to asignal voltage of 4 volts. The variable resistor in amplitude detector58 may be set so that the transistor corresponding to transistor 118responds only if the signal voltage level exceeds 6 volts. Thesefigures, however, of signal voltage levels are merely for the purpose ofindicating relative levels and should not be considered as limiting uponany particular step or of any ultimate magnitude of signal to which thedetectors respond. It is possible to make satisfactory measurements withonly two amplitude detectors and their associated counters.

Because the transistor 118 of amplitude detector 56 is biased to respondto voltage signals above 2 volts in amplitude, the count indicated bycounter 60 which includes solenoid 135 will be a total count of allpulses leaving the direct current amplifier 54 which are in excess of 2volts. Similarly, the counter 61 connected to the output of amplitudedetector 57 will record a count indicative of the number of pulses of atleast 4 volts in amplitude delivered from the direct current amplifier54. Also, pulse counter 62 will record those pulses leaving directcurrent amplifier 54 which equal or exceed 6 volts. Thus the count ofthe counters 60, 61 and 62 will be an indication in digital form ofnumber and relative amplitude of roadbed undulations and thus therelative condition of the roadway under test which in this particularinstance comprises the rails 18, 19 in FIGURE 2.

The advantages of this railway truck inspecting apparatus are numerous.Because the electrical system is provided with a frequency responsivenetwork which rejects or attenuates low frequency signals generated bythe strain gauges in response to car body roll, the requirement for thegyroscopes previously employed to eliminate the effects of car bodyswaying or the requirement of a separate measuring carriage for thissame purpose are obviated. Further, because the strain gauges mounted onthe respective transducers are connected in a bridge circuit toalgebraically combine the resultant generated signals, requirements fordifferential mechanical connection to the respective wheels iseliminated. Still further, because the electrical system is employed toactuate a series of counters through different amplitude responsivecircuits, the count of each counter is indicative of the number ofsignals of that predetermined amplitude which have been generated by thetransducers. This numerical value constitutes a relative indication ofroad conditions which can be quickly recorded and understood by onehaving no previous skill in roadway inspection.

The present invention will thus be seen to effectively accomplish theobjects enumerated herein above. It will be realized that variouschanges and substitutions may be made to the specific embodimentsdisclosed herein for the purpose of illustrating the principles of thisinvention, without departing from these principles. Therefore, thisinvention includes all modifications encompassed within the spirit andscope of the following claims.

What is claimed is: 1. In a dynamic railway track inspecting apparatusadapted to be used on a railway car having a car body, an axle with apair of wheels thereon and truck means mounting said wheels beneath saidbody, the combination comprising electrical means for producingelectrical signals indicative of the difference in vertical movement ofsaid wheels with respect to the car body; frequency responsive means forresponding only to said electrical signals above a predeterminedfrequency; and, indicating means responsive to said signals above saidpredetermined frequency.

2. Apparatus according to claim 1 including amplitude responsive meanscoupled to the output of said frequency responsive means for respondingto those of said signals which have predetermined differences inamplitude and delivering output pulses in response thereto.

3. The combination according to claim 2 wherein said amplituderesponsive means includes a plurality of amplitude responsive detectorseach having an input coupled to said frequency responsive means andwherein said counting means includes a plurality of digital counterseach coupled to the output of one of said amplitude responsive detectorsto give a digital count of the output pulses from each respectivedetector.

4. Roadway level detecting apparatus comprising: electrical means forgenerating a composite wave form indicative of amplitude and frequencyof the difference in vertical movement of a pair of axially alignedwheels relative to a car body supported on the wheels; 1

frequency responsive means coupled to the output of said electricalmeans for delivering an output signal representative of the componentsof said wave form above a predetermined frequency,

amplitude responsive means for delivering output signals indicative ofthe number of times the amplitude of said frequency responsive meansoutput signal eX- ceeds predetermined values.

5. The apparatus of claim 4 wherein said electrical means includes apair of transducer means each coupled to one of said wheels, eachtransducer means including a pair of strain gauges, said gauges beingconnected together to algebraically combine the outputs of said pairs ofgauges.

6. The apparatus of claim 4 wherein said electrical means includes twopairs of strain gauges coupled in a bridge circuit and a direct currentsource coupled to two terminals of said bridge circuit and wherein saidfrequency responsive means includes a high pass filter having its inputcoupled to said bridge circuit and its output coupled to said amplituderesponsive means. v

7. The combination according to claim 4 wherein said amplituderesponsive means includes a plurality of trigger circuits, eachresponsive to a different input signal amplitude and each having itsinput connected to the output of said frequency responsive means.

8. The combination according to claim 7 further comprising a pluralityof counting means each coupled to one of said trigger circuits forcounting the output pulses thereof.

9. In a dynamic railway track inspecting apparatus adapted to be used ona railway car having a car body, an axle with a pair of wheels thereon,and truck means mounting said wheels beneath said body, the combinationcomprising electrical means for producing electrical signals indicativeof the difference in vertical movement of said wheels with respect tothe car body; frequency responsive means for responding only to saidelectrical signal above a predetermined frequency; differentialamplifier means coupled to the output of said filter for producingoutput signals of positive and negative polarity with respect to ground;rectifier means coupled to the output of said differential amplifier forproducing an output of a single polarity in response to input signals ofpositive and negative polarity; amplitude detector means coupled to theoutput of said rectifier means for responding to signals ofpredetermined amplitude; and, counter means coupled to said amplitudedetector means for indicating the number of pulses of predeterminedamplitude delivered from selected ones of said amplitude detector means.

10. In a dynamic railway track inspecting apparatus according to claim9, said electrical means for producing electrical signals indicative tothe vertical movements of said wheels relative to each other comprisinga pair of transducers means each coupled to one of said means, eachtransducer means including a pair of strain gauges, said strain gaugesbeing connected together in a bridge circuit to algebraically bind theoutputs of said pairs of said gauges.

11. The combination according to claim 9 wherein said frequencyresponsive means transmits to said differential amplifier means onlysignals above 2 cycles per second.

12. The combination according to claim 9 wherein said rectifier meansincludes a rectifier bridge coupled to said differential amplifier andto said amplitude detector means.

13. The combination according to claim 9 wherein said amplitude detectormeans comprises a plurality of detector stages each responsive tosignals of different predetermined voltage levels.

References Cited UNITED STATES PATENTS 2,118,105 5/1938 Perry 33 141.5

S. CLEMENT SWISHER, Acting Primary Examiner.

DONALD O. WOODIEL, Examiner.

